Systemic phaeohyphomycosis caused by Veronaea botryosa is regarded as an important emerging mycotic disease of sturgeon aquaculture. However, no vaccines or treatments are currently available. The effects of dietary β-glucan supplementation on resistance to V. botryosa infection was examined in controlled challenges by exposing immunostimulated and control fish to ~7.25 × 105 fungal spores/fish via intra-muscular injection. Six weeks post-challenge, cumulative mortality was determined and antibodies to acute phase-proteins (APP) were used to quantify the conserved APP peptides in the serum of challenged and control fish using Western blot. Transcript levels for all tested pro-inflammatory cytokines, APP, and regulatory cytokines in the spleen were similar amongst treatments at the end of the three-week feeding period. However, significantly higher survival occurred in fingerlings fed 0.3% β-glucans compared to non-immunostimulated fish groups (p < 0.05) six weeks post-challenge. A strong proinflammatory response was detected in exposed treatment groups, and greater survival at 6 weeks was associated with higher transcript abundance of Il-17 in fish fed β-glucans. Findings support the important role of this cytokine in response to fungal infection.
Keywords: Aquaculture; Caviar; Fungus; IL-17; Immunostimulation.
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